Wireless Networks and their Uses
Wireless networks are used to transfer information between two or more spatial locations which are not physically linked. The information may be of any kind, e.g., voice, still or moving images, text and so forth. The information is typically transferred using radio frequency (RF) and/or infrared radiation.
Some of the common types of wireless networks, divided according to coverage area and network topology, are:
(a) Wireless personal area networks (WPANs), such as Bluetooth networks, which interconnect devices within a relatively small area;
(b) Wireless local area networks (WLANs), linking two or more devices over a relatively short distance, usually providing internet connection through an access point;
(c) Wireless mesh networks, whose nodes are organized in mesh topology, in which each node forwards messages on behalf of other nodes. Such networks automatically reroute around faulty nodes;
(d) Wireless metropolitan area networks (wireless MANs), e.g., WiMax, which may connect several WLANs;
(e) Wireless wide area networks (wireless WANs), which typically cover large areas, e.g., between neighboring towns;
(f) Cellular networks or mobile networks, distributed over areas called cells, each of which served by at least one fixed-location transceiver, known as a cell site or base station. Each cell typically uses a set of radio frequencies and/or codes which is different from that of the immediate neighboring cells, so as to reduce interference. When joined together, multiple cells may provide coverage over wide geographic areas, enabling a large number of portable transceivers, such as mobile phones (including smart phones) and pagers, to communicate with each other and with fixed transceivers and telephones anywhere in the network, via base stations. Although originally intended for telephone conversations, cellular networks also routinely carry other types of data, using technologies such as: frequency division multiple access (FDMA), time division multiple access (TDMA), global system for mobile communications (GSM), code division multiple access (CDMA), general packet radio service (GPRS), wideband code division multiple access (W-CDMA), enhanced data rates for GSM evolution (EDGE), CDMA2000, orthogonal frequency division multiple access (OFDMA), and so forth; and
(g) Mobile satellite communications, based on telecommunication satellites. Typically used when other types of wireless connection are unavailable, e.g., in largely rural areas and remote locations, in aviation or in maritime platforms.
The location of mobile devices (e.g., cellular phones) connected to wireless networks is sometimes estimated using these networks. The estimation may be based on measurements made directly by the wireless network infrastructure and/or on external sources of information, e.g., global positioning system (GPS) trackers associated with the mobile devices. For example, US patent application US2012/109853, by Culpepper, Smith and Vancleave, published on May 3, 2012, titled “Method and system for providing tracking services to locate an asset,” discloses a method and system for asset location. Location data is received from a cellular transmitter associated with a selected asset, which location data includes data representative of a cellular receiver with which direct communication with the cellular transmitter is made. The location data is then communicated to a tracking service system, which tracking service system includes a database representative of geographic locations associated with the plurality of cellular receivers. The database is then queried with received location data so as to generate geographic tracking data associated with a location of a cellular receiver, the geographic tracking data including display data adapted to generate a map image including a representative of a location of the selected asset. The geographic tracking data is then communicated to an associated security agency so as to allow for viewing of an image generated in accordance with the display data and at least one of tracking and interception of the selected asset. In some embodiments, location data is also received from a GPS location system associated with the cellular transmitter. Another example is US patent application US2010/120449, by Jakorinne, Kuisma and Paananen, published on May 13, 2010, titled “Method and system for refining accuracy of location positioning,” which discloses a method and system for accurately determining the location of a mobile device. In the mapping phase, collected reference positioning data and collected cell data are used to map a covered area estimation, and in the actual location determination phase, the covered area estimation is calculated from actual environment data received through a wireless cellular communication network, and possibly but not necessarily from external databases. The covered area estimation comprises at least some of the following calculations: (i) estimation of base station location; (ii) estimation of transmission range; (iii) estimation of signal map; and (iv) estimation of area type. The actual location of the mobile device is determined from the covered area estimation based on relative comparison between the actual environment data and estimations (i)-(iv) and weight numbers resulted from the comparison. During both phases, a database is stored in the server and updated whenever new environment data is received. A further example is US patent application US2011/0059752, by Garin, Do and Zhang, published on Mar. 10, 2011, titled “Concurrent wireless transmitter mapping and mobile station positioning,” which discloses a method for concurrently estimating locations for one or more mobile stations and one or more mobile transmitters, said method comprising: receiving at a computing platform a plurality of range measurements from one or more mobile stations with unknown positions, the plurality of range measurements comprising one or more range measurements to one or more wireless transmitters with unknown positions and one or more range measurements to one or more wireless transmitters with known positions; and concurrently estimating locations for the one or more mobile stations with unknown positions and for the one or more wireless transmitters with unknown positions.
Wireless networks can also be used to estimate the location of multiple mobile devices as a function of time. Based on this information, one can create road maps, analyze traffic flow and provide dynamic route guidance for drivers. For example, US patent application US2010/211301, by McClellan, published on Aug. 19, 2010, titled “System and method for analyzing traffic flow,” discloses a system and method for analyzing traffic flow, comprising receiving location reports from a plurality of mobile devices, each of the location reports identifying a current location and current speed for a particular mobile device. For each of the location reports, the system identifies a current street from a street mapping database using the current location. The system stores the current speeds for the mobile devices so that each of the current speeds is associated with a street in the street mapping database. The current speeds may be stored in the street mapping database or in a separate database that is linked to the street mapping database. A further example is US patent application US2010/057336, by Levine, Shinar and Shabtai, published on Mar. 4, 2011, titled “System and method for road map creation,” which discloses a system and method for creation of a road map, the system comprising a plurality of navigation devices; and an application server to receive from the plurality of navigation devices time series of location points, and to create a road map based on the time series of location points. The method comprises receiving location points from a plurality of navigation devices, along with respective time stamps indicating the time of recordation of each of the location points; identifying at least one route according to the location points and respective time stamps; and creating a road map based on the at least one route. A further example is US patent application US2011/098915, by Disatnik, Shmuelevitz and Levine, published on Apr. 28, 2011, titled “Device, system, and method of dynamic route guidance,” which discloses a device, system and method of dynamic route guidance. For example, the method may include: calculating an optimal route from a first location, in which a navigation device is located, to a destination point entered by a user of said navigation device; receiving from the navigation device a travel update, indicating that the navigation device is located in a second location, wherein the second location is on said optimal route; and based on real-time traffic information and real-time road information, determining that an alternate route, from the second location to the destination point, is now an optimal route to the destination point.
Furthermore, mobile devices connected to wireless networks can be used to map network performance parameters as a function of space and/or time. For example, US patent application US2006/246887, by Barclay, Benco, Mahajan, McRoberts and Ruggerio, published on Nov. 2, 2006, titled “Mapping of weak RF signal areas in a wireless telecommunication system using customers' mobile units,” discloses a wireless mobile device, which includes an RF transmitter and receiver, where the receiver monitors signal strength of an RF signal from a base station. A control logic module compares the signal strength to a comparison level. The control logic module creates and stores a record in a memory module. The record includes a first signal strength level and parameters related to conditions existing at the time the comparing was done. The control logic module creates and stores the record if the level of said signal strength is less than the comparison level.
When fixed or mobile devices connected to a wireless network are associated with sensors capable of measuring one or more local physical parameters, the system can be used for detecting events in space and/or in time, e.g., for security purposes. For instance, US patent application US2008/169921, by Peeters, published on Jul. 17, 2008, titled “Method and apparatus for wide area surveillance of a terrorist or personal threat,” discloses methods and apparatuses for the wide area detection of major threats, including chemical, radiological or biological threats, using modified personal wireless devices, such as mobile phones, personal digital assistants (PDAs) or watches, combined with micro- and nano-sensor technologies. A “homeland security” chip is further provided, which combines the elements of geo-location, remote wireless communication and sensing into a single chip. The personal electronic devices can be further equipped for detecting various medically related threats. Similarly modified personal devices can be used to detect external threats that are person-specific. Another example is U.S. Pat. No. 7,952,476, by Causey, Andrus, Luu, Jones and Henry, issued on May 31, 2011, titled “Mobile security system,” which discloses a mobile security system, wherein a detector communicates with a mobile device if an event has occurred. The event may be of various types, such as fire or motion. Once the mobile device receives the communication of the event occurrence, the mobile device may, among others, sound an alarm or communicate with a central monitoring system to notify emergency services of the occurrence. The mobile device may also communicate with another communication device, such as another cell phone or a computer, using various forms of communication. The detector may be an integral part of the mobile device, and may also be wholly separate.
Object Detection Using RF Sensors
Certain methods and systems known in the art employ sensors based on RF radiation for object detection outside the context of wireless networks.
In some systems, the object detection is based on active sensing. For instance, UK patent application GB2473743, by Bowring and Andrews, published on Mar. 23, 2011, titled “Detecting hidden objects,” discloses a system and method for detecting and identifying hidden objects, for instance for airport security screening. Low power plane-polarized microwave radiation is directed towards a person, and scattered radiation is detected by a detector sensitive to polarization in an orthogonal plane (cross-polarization). The transmitted and received planes of polarization are varied, either by rotation of both transmitting and receiving antennas on a common platform, synchronized rotation of both, or switching between antennas having fixed polarizations. The transmitted frequency is modulated over a broad range, using wide-band frequency modulation continuous wave (FMCW). The output signal of the receiver over a period of time is compared with expected returns in a neural network to identify the nature of any hidden object, and can distinguish a large knife, small knife, handgun and so on. An ultrasound sonar or stereoscopic camera may determine the distance to the person. Another example is PCT application WO2009/090406, by Mehta, published on Jul. 23, 2009, titled “Microwave imaging system,” which discloses a microwave imaging system for imaging a defined region, the system comprising a plurality of portable RF identification (RFID) tags, distributed around said region, for generating a plurality of RF signals and directing said signals to said defined region, and for receiving RF signals from said defined region; and means for transmitting the characteristics of said received signals to a remote processing station through a wireless communication channel, extracting image data from said received signals and constructing a corresponding image.
Other systems are based on passive sensing. For example, U.S. Pat. No. 8,179,310, by Westphal, issued on May 15, 2012, titled “Method for sensing a threat,” discloses a method for threat analysis based on the passive radar principle, using the transmitter in navigation satellites, a plurality of receiving stations, which are operated distributed over wide regions, and at least one evaluation center. The receiving stations act as wake-up sensors, transmit their received signals to at least one evaluation center for comparison with expected signals from each navigation satellite, and sense a threat. Depending on the result, stationary or mobile radar systems can then be used to obtain more precise details relating to a conspicuous entity, making it possible to decide on currently required protective or defensive measures. A further example is US patent application US2011/057828, by Brunet, published on Mar. 10, 2011, titled “Mapping method implementing a passive radar,” which discloses a mapping method implementing a radar used in passive mode. It is possible to use such a radar for locating an object likely to reflect an electromagnetic wave transmitted by a transmitter the position of which is known. Movable objects capable of reflecting rays received from transmitters of opportunity are used. The method comprises the following operations: determining, in a distance-Doppler matrix of the radar, points relative to the deviations between the rays received directly from the transmitters and the rays reflected by the movable object; transferring to a map to be established a probable zone of location of singularities of the electromagnetic field transmitted or reflected by the ground; and crossing several probable zones during the movement of the movable object in order to obtain the location of the singularities.
Object Detection Using Wireless Network Infrastructure
Moreover, some methods and systems known in the art perform object detection using wireless network infrastructure. US patent application US2009/0040952, by Cover and Andersen, published on Feb. 12, 2009, titled “Systems and methods for microwave tomography,” discloses systems and methods for microwave tomography. According to various embodiments, signal strength values or other similar quality indications may be analyzed as they are received with packet data over a wireless network. The analysis may be used to determine the presence of a physical object substantially between communicating nodes in a wireless network. An output may be generated based on analyzed data. In addition, U.S. Pat. No. 6,745,038, by Callaway, Perkins, Shi and Patwari, issued on Jun. 1, 2004, title “Intra-piconet location determination and tomography,” discloses a technique for intra-piconet location determination and tomography. This technique uses received signal strength indicator (RSSI) values in conjunction with transmitted power levels to determine the relative location of each device within a small network employing frequency hopped spread spectrum transmission. In addition to capability of location determination, the geometry of the devices in the network, as well as the path loss information between pairs of devices, may be used to infer the location of absorbers and reflectors within the piconet. This absorption and reflection information may be used in creating the piconet tomography. The approach described in this specification may be applied in conjunction with the Bluetooth PAN specification to determine device locations, mitigate the effects of multi-path, and perform indoor location and security functions, and other application functions requiring cost-effective location determination.